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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 180 (Hybrid Energy Storage System) >> Diagnostic Information and Procedures >> DTC P1A1F or P1A4E >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
    WARNING: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
    The High Voltage Disabling procedure will perform the following tasks:
    • Identify how to disable high voltage.
    • Identify how to test for the presence of high voltage.
    • Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.

    Failure to follow the procedures exactly as written may result in serious injury or death.
    IMPORTANT: You must perform the Circuit/System Verification first.
  1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling .
  2. Remove the drive motor generator battery case upper cover and right side cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement .
  3. Connect the 12 V battery.
  4. Ignition OFF, verify 230-407 volts between terminals HV+ at the HV positive relay and HV- at the HV negative relay.
    • If the voltage is between 194-230 volts, perform the jump assist. Refer to Jump Assist .
    • If the voltage is less than 194 volts, replace the drive motor generator battery.
    • If the voltage is greater than 407 volts, replace the drive motor generator control module.
  5. Disconnect the X4 harness connector at the BECM.
  6. Connect the EL-48571  to the X4 harness connector. See Special Tools .
  7. Test for 13-19 volts across all 20 battery voltage reference circuits.
    • if not within the specified range, replace the drive motor battery assembly.
    • If all circuits test normal, replace the drive motor generator battery control module.
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